Experiments are being carried out on neonatal pigs of different ages to study the development of regulation of cardiovascular function. The piglets are lightly anesthetized with halothane and electromagnetic flow probes are placed around the femoral, renal, mesenteric and carotid arteries. These experiments include localization of vasoactive sites in the neuraxis and the recording of blood pressure, heart rate and regional blood flow responses to such stimulation. The effects of the stress of hypoxia on the responses is also under investigation. In addition, in vitro studies of vascular smooth muscle (from different vessels) responses at a variety of vasoactive agents, e.g., norepinephrine, vasopressin, are under investigation. Another study involves recordings of spontaneous sympathetic activity in these young animals.